What are the FOV parameters of an LX90

[Rohan]

Hi,

I've been using Starry Night Pro 5 recently and it has the option to input eyepieces and scope details which it can then project over the sky maps to show the user what they should be seeing through any given eyepiece (see attached image).

So what i want to do is have one for my LX90 with no eyepieces so i can get an idea of what the FOV will be when i have a SLR attached at prime focus. Anyone know what parameters it may be. I have options to enter "type of eyepiece' ie. plossl, 'eyepice diameter' and the 'aperature field of view'. The default aperature field of view is 50deg. I have used this when entering my bintel plossl eyepieces. Should this be another figure?

Cheers in advance and i highly recommend the program for telescope control and such.

[[1ponders] (Paul)]

here ya go Rohan. From "Astrophotography for the Amateur"

This is for 35 mm film, so there is probable a 1.5X adjustment for canon ccd
Focal length to field of view
400mm = 3.4 degX 5.2 deg
500mm = 2.7 X 4.1
600mm = 2.3 X 3.4
800mm = 1.7 X 2.6
1000mm = 1.4 X 2.1
1250mm = 1.1 X 1.7
1500mm = 0.9 X 1.4
2000mm = 41' X 62'
5200mm = 33' X 50'
3000mm = 28' X 41'
4000mm = 21' X 31'
5000mm = 17' X 25'
6000mm = 14' X 21'
8000mm = 10' X 15'
15000mm = 5.5' X 8.3'
20000mm = 4.1' X 6.2'

Now from what I understand if your using the canon then you need to multiply your FL by 1.5 to bring it inline with 35 mm film. This may mean you need to divide the fields of view to bring them into comparison. I'm sure someone else here would be able to make that clearer
Cheers

ps there is a formula for working it out if you have a different focal length, but its only withing 1% accuracy if your FL is over 1000mm
Field of View = 57.3 x (w/F) degrees, where w is the width or length of your film and f is the focal length of your scope. Again from "Astrophotography for the Amateur"

[h0ughy (David)]

are you using a focal reducer as well? that should widen things out a little

[Rohan]

well havn't actually got the camera yet. Just starting to experiment with the software to what i'll be able to capture.

[acropolite (Phil)]

What Paul says makes sense because the cmos sensor on the EOS is smaller than 35mm film the corresponding FOV will be smaller so you shoud divide the fov by 1.6 Have you got an adapter and T ring yet Rohan if not Scopestuff in the US have a shorty adapter which fits the canon perfectly, allowing full clearance from the forks (although not with a focal reducer)??

[Rohan]

Cheers Phil, will keep that in mind when i purchase. at this stage prob going to be a tax return buy (if i get anything half decent)

[[1ponders] (Paul)]

Rohan if you can find out the dimensions of the cmos chip you can insert each one into the above formula (w) to get a more accurate field of view for the chip

[Rohan]

22.2 X 14.8mm according to a canon brochure i have.

[Starkler (Geoff)]

Basic trigonometry:
artan(ccd width/focal length)

0.63 x 0.42 degrees is what I come up with.